Process for producing lamelliform metal powders



Dec. 16, 1930. 1,785,283

PROCESS FOR PRODUCING 'LAMELLIFORM MET AL PbWDERS E. FODSZUS Filed Sept. s, 192:

Patented 'Dec. 16, 1930 UNITED STATES PAT Nroi-ncE EMIL ronszus, or BEBLIN-FRIEDRiCHsHAFEN, GERMANY, nssrenon T min'rsrorr- METALL AKTIENGESELLSCHAFT (HAMETAQ), or BERLIN-COPENICK, GERMANY rnocnss ron rnonucme LAMELLIFORM METAL rownnas Application filed September 6, 192's, Serial'No.

My invention relates-to a process and de vice for converting fine metal particles into minute leaves, preferably such having a bright lustre as required in the manufacture of so-called bronze paints.

Thevariousattempts heretofore made to flatten. fine metal particles, as for instance by means of rollers, have not been successful.- The cause of such failure was, in the first place, due to the insuificiency of the means employed, in view of the extreme fineness of the powder, the size of the grain amounting, for instance, to one thousandth part of a millimetre.

According to my invention one can flatten and polish even very fine metalpowder and at the same time produce a lustre on the surface of the flat metal particles. lhis'I achieve by so constructing the apparatus for flattening the metal particlesthat' a sufliciently close contact between the work ing-surfaces of the operating elements takes place to produce the desired'success.

' Of further importance is the quantity of the metal powder supplied in proportion to the size and dimensions of the operating surfaces of the apparatus.

If an excessively large quantity is fed into the apparatus, the metal particles are-heaped. Q on top of each other thereby forming, so' to say, an elastic. cushion which more or less prevents-the flattening process. The best result is obtained, if the operating elements are covered with rather a thin layer of particles only and more preferably only with a layer of particles onthe effective surfaces.

Fu thermore the period during which the fiattex iing operation takes place greatly affects the quality of the product.

Because of the accuracy required of the operating elements and the greatcost en- 1 tailed thereby, it seemed desirable, of course, to reduce their number as much as possible and in consequence thereof, to allow" the metal-particles to be subjected for a longer I period to the action thereof, on the assumption that during such extended period a flat-' tening of all particles could be effected Experiments have proved, however, that such a method does not produce a good result.

correct co-operation between 661,331, and in Germany September 12, 1922.

Moreover, the product will be a powder, a portion of which has not been flattened at all, while another portion has become compacted into large lumps, and that a small proportion. only has received the desired flattened shape.

To reventacompacting of the metal particles, he pressure between the operatingelements must be suited to the hardness or toughness of the metal particles tobetreated. It is therefore preferable to provide the operating elements with the greatest possible surface, in order to'shorten the period of the working process, which, however, involves the disadvantage that the apparatus must be made of a considerable size.

According to my invention, however, this latter disadvantage is avoided in a simple manner.

In the drawing, the diagrammatic Figures 70 1 and'2 fully explain the above mentionedconditions with'regard to the shape of the operating elements, while Figure 3. shows, by way of example, an embodiment of apparatus for carrying out thenew process. '15 Figure fill'ustrates the, mode of action of a device, where, in one instance the proportions in the size of thewarious parts are not in har-- mony with each other due to deficiencies in manufacture, while in the other instance a 5o the operating elements is achieved.

Even. thothe workingfaces of the operating elements have been prepared as carefully as possible, certain inaccuracies cannot 'be avoided. Generally, it may be said that already a. great accuracy in the manufacture has been reached where the device approaches within one hundredth of a millimetre the mathemati'cally'correct shape, that is to say, the inaccuracies are below the limit of one hundredth of ami'llimetre and may. therefore amount to nine thousandth of a millimetre, I that is to say, nine grains of the size of one thousandth of a millimetre can slip by simul- '95 I taneously without having been acted upon by the operating elements. If by chance such an unevenness comes to be opposite a similar inaccuracy of the co-operating element, naturally the double quantity of particles can slip through the opening thus enlarged without being gripped by the elements. Thelarger the surfaces of the opposed Working elements, the greater will be this danger. It

is therefore advisable in order to'avoid the;

disadvantage accompanying these inaccuracies, to make the working elements as far as' possible of such a shape thatmathematic-ally speaking they touch each other along one line .or, still better, in one point only. The first condition occurs, for instance, where a roller cooperates with a plane or curved surface, while the latter condition is present, where instead of a roller a ball is employed. This expedient will however not give the desired result, unless the ratios of the sizes of these elements are of the right proportion. In the dlagrammatic Figure 1, 1 denotes a plate the inaccuracies of which have been exaggerated.

If .on this plate a roller or ball 2 of the size shown is allowed to roll, it is inevitable that between the roller or ball and the recesses in the plate 1, for instance in the position as shown, a hollow space 3 will he -formed in which the metal particles to be flattened are wholly or partially out of reach of the roller or ball 2.

When looked at mathematically, this is due to the fact that the radius of curvature of the roller or ball 2 is greater than that of the-unevenness in the surface of the plate 1. The

. unfavourable effect is still further increased,

if corresponding inaccuracies also exist in the roller or ball 2.

Therefore, I make the radius ofcurvature of the roller or ball correspondingly smaller as indicated at 4. 'The formation of inactive. hollow spaces 3 is thereby avoided and the metal particles can be acted upon in the desired manner.

The conditions are of course, quite similar if also the element 1, as shown in Fig re. 1s given a curved surface.

In accordance with my invention, also elastic operating elements may be used adapted to be compressed so that no holes are formed by the cooperating surfaces. Since only comparatively slight inaccuracies are to'be considered, a slight degree of elasticity of the working faces of the operating elements will suffice, or one of the elements only is. made I'lgid, while the other is made elastic. The

operating elements may, for instance, be made I of fairly hard rubber, or of hard rubber, galalithe or the like. For obtaining a suificiently According to the size of the apparatus and I the exactness of its manufacture the sizes of the various elements are best determined by experiments.

Also the quantity of the metal particles to be treated is best determined by experiments.

It is of. importance that no great amount of metal particles accumulates between the working faces, because otherwise the flattening'proces's is hindered. To cause fresh particles to pass between the working elements, I accomplish in a particularly simple manner by whirling up the particles of powder in an atmosphere of gas, powder or liquid with which the apparatus is completely or partly filled. The process is particularly successful, if the particles subjected to the operating elements are immediately whirled up, while the descending particles are worked.

- A very good result is obtained, if the metal particles are not only rolled, beaten or hammered, but simultaneously also a sliding movement between the working elements takes place. In this way, the surface of the 'metal, particles is polished and an increased lustre is obtained. Witlly process, it is of advantage depending on t e-condition of the metal powder to-be worked, to add thereto small quantites of fat, oil and the-like, as

thereby the polishing process is aided and the danger of a caking of the particles is reduced.

At any rate, an injurious rubbing between the metal particles or between the metal particles and the operating elements must be avoided, as such rubbing would lead to an excessive disintegration of the metal particles whichwould tend to result in a blackening of the powder.

It must further be avoided that between H the elements used for flattening no injurious rubbing takes place which will cause a wearing away of theworking elements and a consequent contamination of the powder.

For-the flattening there may be used 9.0- I

cording to my invention devices with which,

for instance, a number of small hammers or the like are employed which are pressed against the co-operatiiig surface by their own weight or by means of springs and which are movablymounted in a suitable manner.

A simple and efficient apparatus for practising the process is showndiagrammatically in Figure 3. I

It consists of a drum 11 rotatably mounted on an axle 12. This drum 11 is fitted with a series of partition walls 13 which partly extend inwardly, preferably in the direction towards the axle 12. This'drum is charged with the suitable quantity of metal particles to be flattened and with the correct number ofsteel balls 14 of the right diameter. The

drum is then rotated about the axle 12.

The-quantity of the powder and of the steel balls required is preferably fixed by experiments. At any rate, only a part of the drum 11 may be filled by both of them. Upon the ticles for use in'the manufacture of bronze rotation of the drum 11, the metal particles paints, comprising subjecting the partlcles of and steel balls are mixed with each other, and previously finely comminuted metal to. coneach time,'both are advanced by the partition .tinual impact between a large number of walls 13 until in consequence of the increastiny steel balls by imparting to said steel balls 'time the desired flattening of the various metal particles takes place between the balls and the drum with its partition walls.

By making the various parts of the right dimensions in proportion to each other and by using the proper quantities of metal particles and balls, an exceedingly good and comparatively quick flattening of the various particles is achieved, in spite of the device being of'an extremely simple construction.

The partition walls 13 also advance the metal particles and drop them in a similar manner as is done with the steel balls until they have been turned up to a sufiicient extent. In this waythe powder is whirled up, and fresh particles constantly pass between the steel balls or between the steel balls and the wall of the casing respectively. In this case, the intensity .of the stroke exerted by r the steel balls can be adjusted within a wide range by the speed of the drum 11 with the. partition walls 13. Apart therefrom, the height and intensity of the drop of the steel balls depend upon the number of the partition walls 13.,and upon their width.

It has been shown by experiments that.

with the aid of steel balls-having a diameter of from 3 to 5 millimetres, very good results are obtained. These numerous balls supply a large working surface so thatca fine dis-' 'tribution of the powder over the various working surfaces takes place.

The number of balls used varies, of course,

. depending on their size, i. e. their diameter,

and the kind of metal to be converted into powder. As the volume rather than the weight of the metal determines the number of balls used, a greater number of balls, for

instance, is used in the case of aluminum than in the case of copper.

The device may, of course, be modified in many ways without departing from the nature of the invention.

- Thus, for instance, the cylinder 11 maybe made st tionary, while the walls 13 are rotat-- :able only. I I claim as my invention:

, L'The method of producinga lustrous metal roduct composed of lamelliforin particles' or use in the manufacture -0 bronze paints, comprising subjecting the particles of previously finely comminuted metal to continual impact between a. large number of tiny steel balls by imparting to said steel balls a revolving motion.

2,! The method of producing a lustrous metal product composed of lamelliform par ing inclination of the various partition walls a revolvingmotion, and causing said steel 13 they slide off and drop down.- At the same balls to continually drop upon said par icles.

. EMIL PODSZ s. 

